For traditional Ziegler-Natta catalyst for olefin polymerization to produce an unimodal or bimodal product, the control of branching (comonomer) distribution by modifying this catalyst is quite difficult. Metallocene or single-site catalysts can dramatically change the distribution, and their technologies to produce fully functional unimodal/bimodal resin have recently been commercialized. For example, high performance bimodal polymers require a resin with very few branches in the lower molecular weight fractions and high concentration in higher molecular weight fractions. Such a control of comonomer distribution is important for resin grades such as pipe applications that require excellent environmental stress crack resistance (ESCR).
Since metallocene catalysts have been introduced, the number of advantages in the production of polyolefin copolymers using these catalysts offer a number of advantages including improved activity compared to traditional Ziegler Natta catalyst. Again metallocene catalysts are often described as being single-site in nature, the polyolefins produced with these catalysts are often very uniform in their molecular structure.
It is also well known that metallocene catalysts have been used for olefin polymerization to obtain a desired product.
Many metallocene catalysts have been disclosed. EP 0783022 B1 discloses the preparation of ethylene plastic using metallocene catalyst. EP 1598378 A1 also discloses a process for preparation of a multimodal polyethylene using metallocene catalyst.
EP 0971962 relates to a process for the polymerization of an olefin monomer and one or more comonomers to produce a polymer using a supported olefin polymerization catalyst system produced from catalyst component comprising a support material, a metallocene complex having transition metal of zirconium, and an activator.
EP067103 B2 relates to a ready-for-use supported olefin polymerization catalyst prepared by impregnation to obtain metallocene catalyst, Cp2ZrCl2, biscyclopentadienyl zirconium dichloride in MAO solution with an inorganic oxide as a catalyst support.
WO 00/40620 relates to bimodal polyethylene preparation using metallocene catalyst of either a bridged siloxy substituted bisindenyl zirconium dihalide compound or a catalyst comprising a monoalkyl substituted biscyclopentadienyl hafnium compound.
EP605952 discloses a process for producing polyethylene using metallocene catalyst such as bis(1,3-n-butyl cyclopentadienyl) zirconium dichloride and bis (1,3-dimethylcyclopentadienyl.
U.S. Pat. No. 6,242,545 relates to a process for the polymerization of monomer using hafnium transition metal metallocene catalyst. The hafnocene comprises at least cyclopentadienyl ligand including at least one linear or isoalkyl substituent of at least 3 carbon atom.
Even though the metallocene catalyst for olefin polymerization process is known and has been described, there is still a need for developing novel effective metallocene catalyst for olefin polymerization process.
Accordingly, it would be desired to provide an alternative metallocene catalyst within simple preparation and competitive cost. Further, an olefin polymerization catalyst shall be provided, having increased activity and allowing better control of branching of the polymer as well as of comonomer incorporation and distribution.
Further objective to be solved by the present invention are precise olefin polymerization, especially the evolution of new polymers with specified functions.